|"Sir Maurice Wilkes" from an article in Personal Computer World|
Even today, if you have a sense of history, you can get a shiver down your
spine running the first code of the world's first operational general-purpose computer. Any novice
programmer knows the thrill of getting code to run for the first time.|
The team who built the Electronic Delay Storage Automatic Calculator (Edsac) at Cambridge University had been doing nothing so simple as tweaking a few lines of code: they had spent more than three years building the computer and learning to program it from scratch. Suddenly, after months of debugging, it worked: a teleprinter began printing out a table of squares. It was 6 May 1949, and you could see it as the beginning of the modern world. The Edsac kept going for nearly 10 years, but the man responsible for it is still going, rather more strongly than you would expect at the age of 89.
In 2003 Sir Maurice Wilkes drives daily to the Cambridge Computer Laboratory, where he has an office as emeritus professor, and his mind is as agile as ever. There are of course other people and other times with a claim to having given birth to computing. There was the Victorian engineer Charles Babbage, who described and tried to build programmable computing machines a century before the technology had matured enough to make them practical.
His work had been largely forgotten by 1937, when young Wilkes began work at the Computer Lab, then known as the Mathematical Lab, under Sir John Lennard-Jones, a structural chemist who was interested in using machines to solve differential equations.
A year earlier, Alan Turing had published his classic paper, On Computable Numbers, outlining a universal computing machine. But Wilkes recalls:
'It was purely theoretical. There is no hint in that paper of there being any practical applications. No hint whatsoever. I think he [Turing] made that connection afterwards.'
Computing at the lab involved mechanical desk calculators and analogue computers that solved mathematical problems by modelling them mechanically - just as an analogue clock 'computes' the time by modelling the rotation of the earth. There was nothing that is generally thought of as a computer today. 'No-one had thought of digital computers. That was all in the future,' said Wilkes. So, as it turned out, was his work on computing.
Wilkes, who had done his doctorate on radio waves in 1934, became a wartime boffin, pulled from the lab to work on radar even before hostilities started. When he returned to Cambridge after the Second World War, he found himself in charge of the laboratory. 'It was wonderful. I'd had six full years involved in radar and I got away as soon as I could and said to myself: "Let's do something constructive." There was a wonderful feeling of reconstruction in the world. Everyone felt this excitement of establishing peacetime values.'
Considerable steps had been made in computing during the war. A team under mathematician Max Newman built a proto-computer called Colossus at Bletchley in 1943 to help decrypt signals; Turing, of course, also worked there. Colossus could perform logical operations but no arithmetic, and the fact that Britain insisted on keeping it secret for 30 years limited its influence. Much more important to Wilkes was the 18,000-valve Electronic Numerical Integrator and Automatic Computer (Eniac) completed in 1945 in the US by a team led by Presper Eckert and John Mauchly, initially to perform artillery calculations. It was decimal rather than binary, it was very cumbersome to program, and the processor was not separated from the memory. but a lot of lessons were learned building it.
Out of the blue in 1946 Wilkes got an invitation to attend a series of lectures at Philadelphia's Moore School involving the Eniac team leaders. 'It was very difficult to cross the Atlantic at the time. Shipping was very scarce. But I did get there for the latter part of the course and I got the whole story - all these new ideas. As far as I am concerned that is where they all came from,' Wilkes said. 'They were quite revolutionary. The idea that everything could be contained in memory: numbers, any mathematical tables that you needed, and indeed the program itself. All contained in one big memory. No setting up the machine. You walked up to it, you fed your program in, and then you were in business. You didn't have to set a lot of switches, or knobs, or things of that sort. In fact it was the idea of the modern computer.' In contrast to the secrecy surrounding Colossus there was a 'very free exchange of information'. Wilkes recalled: 'I came back from that course feeling that I knew everything there was to know. Some of the people on the course, and some others, set about building computers. The Edsac was one of these [projects].
A major technical problem was how to implement fast memory. At Manchester University, FC Williams and Tom Kilburn solved the problem by using a cathode ray tube. Their 'Baby' was working
before Edsac but it was a short- lived pilot project.